Polyethersulfone composite hollow-fiber membrane prepared by in-situ growth of silica with highly improved oily wastewater separation performance

In order to reduce surface aggregation and enhance the performance of PES membranes, a hydrophilic PES/TEOS HF membrane was developed for the treatment of wastewater containing oil. PES/TEOS was prepared via a sol-gel self assembly and dry–wet spinning method. Silicon dioxide sol was prepared from a mixture of tetraethoxysilane, ethanol, water, and acetic acid (acting as the catalyst). HF hybrid membranes were produced from dope solutions containing polyethersulfone, polyethylene glycol, silicon sol, and NMP. The membranes were characterized by field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX), porosity, fourier transform infrared spectroscopy (FTIR), and contact angle measurements. The composite membranes were successfully used to treat wastewater containing oil and their separation performance were evaluated. The PES/TEOS-2 membrane displayed the best performance, with a permeate flux of 90.937 L/m² h and an oil retention of 99.98%. In addition, this membrane showed a higher pure water flux of 102.43 L/m² h as compared to PES-0 and PES/SiO₂–1 membranes (87.347 L/m² h and 91.949 L/m² h, respectively). The PES/TEOS-2 membrane also presented enhanced antifouling behavior with a FRR and a RFR of 93.33% and 11.22%, respectively. In addition, this membrane displayed excellent long-term recycling properties, making it a desirable candidate for oily wastewater separation applications.     

Recycling of waste attapulgite to prepare ceramic membranes for efficient oil-in-water emulsion separation

Large-scale application of ceramic membranes is restricted by high cost resulting from raw materials and sintering process. In this study, low-cost ceramic membranes were prepared with waste attapulgite (WAT) and α-Al₂O₃ as starting materials and used for oily wastewater treatment. The optimal membrane sintered at 1100 °C possessed excellent properties, with open porosity of 41.6%, flexural strength of 37.2 MPa and average pore size of 0.40 μm. The membrane also displayed outstanding permeability and chemical stability. The hydrophilicity and underwater oleophobicity were enhanced after surface modification. When used for oil-in-water emulsion filtration, the permeate flux reached 236.8 L m^?2 h^?2 bar^-1 under a low transmembrane pressure of 0.2 bar and the oil rejection exceeded 99%. Membrane cleaning with a simple ultrasonic treatment could easily achieve flux recovery. This study proposed a feasible strategy for both solid waste utilization and oily wastewater treatment.     

Electrospinning superhydrophobic–superoleophilic PVDF-SiO2 nanofibers membrane for oil–water separation

Oil–water separation has attracted research interest due to the damages of oily wastewater caused to the environment and human beings. Electrospun fiber membrane has high oil–water separation performance. A nanofibers membrane with multi-stage roughness was prepared by electrospinning using poly(vinylidene fluoride)(PVDF)-silica blend solution as raw material. The result shows that the water contact angle (WCA) of the nanofibers membrane was promoted from 138.5 ± 1° to 150.0 ± 1.5° when the SiO₂ content was increased from 0 to 3 wt%. The nanofibers membranes exhibited excellent separation efficiency (99 ± 0.1%) under gravity drive, with high separation flux of 1857 ± 101 L·m⁻²·h⁻¹. More importantly, the obtained PVDF-SiO₂ nanofibers membranes showed excellent multi-cycle performance and stable chemical resistance, which would make them great advantages for the practical application of oil–water separation.     

Effect of PVP Molecular Weights on the Properties of PVDF-TiO2 Composite Membrane for Oily Wastewater Treatment Process

Polyvinylidene fluoride (PVDF) hollow fiber ultrafiltration membranes consisted of TiO₂ and different molecular weight (M_w) of polyvinylpyrrolidone (PVP) (i.e., 10, 24, 40, and 360 kDa) were prepared to treat synthesized oily wastewater. The membrane performances were characterized in terms of pure water flux, permeate flux, and oil rejection while their morphological properties were studied using SEM, AFM, and tensile tester. Results show that the PVDF-TiO₂ composite membrane prepared from PVP40k was the best performing membrane owing to its promising water flux (72.2 L/m².h) coupled with good rejection of oil (94%) when tested with 250 ppm oily solution under submerged condition. It is also found that with increasing PVP M_w, the membrane tended to exhibit higher PVP and protein rejection, greater mechanical strength, smaller porosity, and a smoother surface layer. Regarding the effect of pH, the permeate flux of the PVDF-PVP40k membrane was reported to increase with increasing pH from 4 to 7, followed by decrease when the pH was further increased to 10. Increasing oil concentration in the feed solution was reported to negatively affect the water flux of PVDF-PVP40k membrane, owing to the formation of thicker oil layer on the membrane surface which increased water transport resistance. A simple backflushing process on the other hand could retrieve approximately 60% of the membrane original flux without affecting the oil separation efficiency. Based on the findings, the PVDF-TiO₂ membrane prepared from PVP40k can be potentially considered for oily wastewater treatment process due to its good combination of permeability and selectivity and reasonably high water recovery rate.     

Preparation and characterization of nanofiltration membranes fabricated from poly(amidesulfonamide), and their application in water–oil separation

Nanofiltration membranes prepared from selected types of poly(amidesulfonamide) (PASA) targeted to retain either sucrose, raffinose, or β‐cyclodextrin were fabricated in conditions deduced from a chemometric method. Membrane performance was characterized by the permeation of solutions containing 1000 ppm carbohydrates and metal ions. To demonstrate the dependence of the membrane properties on the polymer structure, the separation characteristics of a series of four PASA homopolymers and four PASA copolymers were established. The results allowed us to screen out several promising PASA materials for the NF separation process. In addition, the superiority of the PASA materials, characterized by excellent retention and high flux rate, was evident from the results of a study comparing it with polysulfonamide, poly(ether amide), and commercially available regenerated cellulose. As a means of pollution control, the PASA NF membranes have been proven to be effective in removing oil from oily wastewater. Under an operating pressure of 2–3 psi, a constant flux of 5 L m^?2 h^?1 and 99.6% retention of a solution of 5000 ppm olive oil could be achieved with the PASA membranes over a period of 430 h. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1803–1810, 2003     

Preparation and applications of microfiltration carbon membranes for the purification of oily wastewater

Microfiltration carbon membranes for oily wastewater treatment were fabricated from phenolic resin. The effects of oil concentration, running time, additives and regeneration on the removal of oil from wastewater were investigated. The as-obtained microfiltration membranes possess a macroporosity of 39.0% and meso and microporous volumes of 0.134 m³/g, along with two major pore size distributions around 0.1 μm and 20 nm. They are, respectively, attributed to the constituted particles’ stacking and the precursor pyrolysis. The results showed that the microfiltration membranes can efficiently remove the oil in wastewater. In the presence of ethanol as an additive in solution, the oil concentration is dramatically reduced from initial 200 mg/L in feed to below 10 mg/L in permeate, with an oil rejection of 95.3%.     

Processing of alumina‐coated glass‐bonded silicon carbide membranes for oily wastewater treatment

Crack‐free γ‐Al₂O₃‐coated glass‐bonded SiC membranes were successfully prepared using a simple heat‐treatment and dip‐coating process at a temperature as low as 850°C in air. The changes in the porosity, flexural strength, flux, and oil rejection rate of the membranes were investigated while changing the initial SiC particle size. Larger SiC particles led to bigger pores, resulting in higher flux in the oily water and a lower oil rejection rate. The SiC membranes with a support prepared from 10 μm SiC powder showed an exceptionally high oil rejection rate (99.9%) with a feed oil concentration of 600 mg/L at an applied pressure of 101 kPa. The typical porosity, flexural strength, steady state flux, and oil rejection rate of the alumina‐coated SiC membrane were ~45%, ~81 MPa, 1.78×10^?5 m³ m^?2s^?1, and 99.9%, respectively.     

Synthesis,characterization and performance evaluation of an optimized ceramic membrane with physical separation and photocatalytic degradation capabilities

The main goal of the present study is synthesis, characterization and performance evaluation of an optimized photocatalytic ceramic membrane for wastewater treatment. It consists of three layers including alumina (Al₂O₃) macroporous support, colloidal titania (TiO₂) mesoporous intermediate layer and polymeric TiO₂ mesoporous top layer in order to obtain a pore gradient from the support through the top layer of membrane. The colloidal and polymeric TiO₂ layers were prepared via the sol-gel method and coated using sol dip-coating approach. In order to optimize the membrane, physical separation and photocatalytic degradation capabilities of each colloidal and polymeric layer as a function of time were evaluated using Rhodamine B (RhB) aqueous solution. Thus, optimum coating number of intermediate layer and top layer were determined. Also, the performance of the optimized membrane was investigated via oily wastewater treatment using crude oil and water emulsion. Based on the performance results, two consequence colloidal layers and one polymeric layer were considered as the optimum layer number. Also, RhB photocatalytic degradation was 24.7% and RhB physical separation and permeation flux were 40.4% and 25.7?kg?m^?2 h^?1, respectively. Furthermore, based on the oily wastewater treatment experiments, permeation flux and chemical oxygen demand (COD) rejection at the best-operating conditions (pressure of 5?bar, the temperature of 30?°C and cross flow of 600?l?h^?1) were 29.1?kg?m^?2 h^?1 and 78.4%, respectively. The prepared membrane was found efficient and exhibited high industrial potential due to its multifunctional capability and thus can be employed as an advanced material for wastewater treatment applications.     

Superhydrophilic–underwater superoleophobic TiO<Subscript>2</Subscript>-coated mesh for separation of oil from oily seawater/wastewater

Oil/water separation is a topic of interest worldwide because of increasing release of industrial oily wastewater and frequent leakage of crude oil. Superhydrophilic and underwater superoleophobic meshes were fabricated by simple and fast dip-coating of nanosized TiO₂ on a stainless steel mesh with a 50 μm pore size. The coated mesh was used for oil/water separation by gravity-driven filtration without additional energy. After acid treatment and TiO₂ coating of the mesh, its surface property was altered from hydrophobic to superhydrophilic and superoleophobic. Oil/water separation was achieved in 3 s with an efficiency of 98–99%, irrespective of oily water type (seawater or wastewater). Initial separation efficiency was maintained during a test involving 20 recycles. Therefore, the as-made TiO₂-coated mesh can be used in practical applications such as for wastewater purification, and in the petroleum industry.     

Solution-blow spun PLA/SiO2 nanofiber membranes toward high efficiency oil/water separation

With the ever frequent of industrial organic solvent emissions and oil spillages, the development of high efficiency oil/water separation materials has attracted extensive attention. Here, PLA-based nanofiber membranes modified with metal oxides (SiO₂, TiO₂, Al₂O₃, and CeO₂) are fabricated through blow spinning the mixed solution of polylactic acid (PLA) and metal oxide nanoparticles (NPs). Results shows that the addition of SiO₂ NPs significantly increases the hydrophobicity of the membranes, while maintaining the excellent superoleophilicity. The PLA/SiO₂ nanofiber membranes demonstrate a higher separation performance than pure PLA, PLA/TiO₂, PLA/Al₂O₃, and PLA/CeO₂ nanofiber membranes with high separation efficiency (~100%) and permeation flux (17,800 L m⁻² h⁻¹ for n-heptane), as well as prominent oil adsorption capacity (19.9 g/g for n-hexane). The successful fabrication of metal oxides modified PLA nanofiber membranes with high separation and adsorption ability, and excellent durability hold great application potential in the field of oily wastewater treatment.     

Performance of Low Cost Ceramic Microfiltration Membranes for the Treatment of Oil-in-water Emulsions

Using the uniaxial compaction method, ceramic disk type microfiltration membranes were fabricated using mixtures of clays to yield membranes M₁, M₂, and M₃. These were obtained with distinct compositions of raw materials at a sintering temperature of 900°C. Membrane characterization was conducted using thermogravimetric analysis (TGA), particle size distribution (PSD), X-ray diffraction (XRD), and scanning electron microscope analysis (SEM). Morphological characterization of these membranes includes the evaluation of average porosity, pore size, mechanical stability, chemical stability, and hydraulic permeance. With varying composition of the raw materials, it is observed that the average porosity and pore size of the membrane varied between 23–30% and 0.45 to 1.30 µm. For all membranes, the flexural strength varied within the range of 10-34 MPa. Chemical stability tests indicate that the membranes are stable in both acidic and basic media. The hydraulic permeance of M₁, M₂, and M₃ membranes is about 3.97 × 10^?6, 2.34 × 10^?6, and 0.37 × 10^?6 m³/m² s kPa, respectively. Further, the performance of these membranes was studied for the microfiltration of synthetic oily wastewater emulsions. Amongst all membranes, membrane, M₂ performance is satisfactory as it provides oil rejection of 96%, with high permeate flux of 0.65 × 10^?4 m³/m² s at a lower transmembrane pressure differential of 69 kPa for the oil concentration of 200 mg/L.     

β-SiAlON ceramic membranes modified with SiO2 nanoparticles with high rejection rate in oil-water emulsion separation

Porous ceramic membranes with high mechanical strength are suitable for oil-water emulsion separation. Nonetheless, it is difficult to prepare ceramic membranes with a small pore size and a good antifouling ability. In this work, SiO₂ nanoparticles were used to modify β-SiAlON ceramic membranes, which were successfully utilized to remove small oil droplets from oil-water emulsion. The modified membranes displayed a narrow pore size (the average pore size decreased from 1.05?µm, in the unmodified membrane, to 0.65?µm), and gas and water fluxes which are suitable for oil-water separation. Oil rejection rate was always higher than 90% under various pressures (1.0–2.0?bar) and flow velocities (1.0?3.0?L?min^?1) tested, which is considerably higher (60%) than the rejection rate of the unmodified membrane (which was 39.8%). Moreover, the modified membranes exhibited a good antifouling ability, since flux declined by only 7.0% after three recoveries via a simple ultrasonic treatment, over a total running period of 10?h. Accordingly, the produced membranes can be qualified for further consideration in oily wastewater treatment.     

An oil-contamination-resistant PVP/PAN electrospinning membrane for high-efficient oil–water mixture and emulsion separation

Oil–water separation is an urgent issue due to the frequently occurred oil leakages and increasing discharge of oily wastewater. The pollutional and wastewater can not only damage the environment, but endanger human health. Owing to the small particle size of the oil contamination, it is still a challenge for the separation of oil–water emulsion. In this study, we developed a facile strategy to prepare a hydrophilic polyvinylpyrrolidone/polyacrylonitrile (PVP/PAN) nanofibrous membrane for oil–water mixture and emulsion separation. The lowest water contact angle on the membrane surface can achieve 16.7°, thus the membranes can effectively resist the oil contamination on them. Moreover, the membrane can efficiently separate oil–water mixtures and emulsion by gravity. In addition, it can separate oil–water mixtures in harsh conditions (pH = 1 and 14). Membranes prepared in this work would hold a great potential in the practical use of water treatment and environmental industry.     

Biological treatment of high salinity produced water by microbial consortia in a batch stirred tank reactor: Modelling and kinetics study

This study was performed to evaluate the potential of acclimated halophilic microorganisms, commercial microorganisms, and microorganisms from polluted soil to degrade crude oil in high salinity oily wastewater (synthetic produced water) at different salt concentrations ranging from zero to 250,000?mg?L^?1 of total dissolved solids (TDS). The highest degradation of crude oil (>60%) was found for acclimated halophilic microorganisms at TDS of 35,000?mg?L^?1. An increase in the TDS concentrations above 145,000?mg?L^?1 leads to a significant decrease in the growth of microorganisms. The results showed that efficiency of the commercial microorganisms was less than the acclimated halophilic microorganisms. The oil biodegradation followed substrate inhibition kinetics and the specific growth rate were fitted to the Haldane model. The biokinetic constants for the saline oily water at TDS of 35,000?mg?L^?1, i.e., Y, K_s, µ_max, and 1/K_i, were 0.21?mg?MLSS/mg crude oil, 0.27?mg?L^?1, 0.019?h^?1, and 0.002?mg?L^?1, respectively.     

Sulfonated polyethersulfone by heterogeneous method and its membrane performances

Polyethersulfone was sulfonated by heterogeneous method with chlorosulfonic acid. Ion exchange capacity was controlled to 0.68 meq/g to reduce fouling. Sulfonation was confirmed by Fourier transform infrared spectroscopy and ¹H‐nuclear magnetic resonance. Polyethersulfone and sulfonated polyethersulfone ultrafiltration membranes were prepared successively by the typical phase inversion method. Membrane performance of sulfonated polyethersulfone was compared with that of polyethersulfone. In the preparation of ultrafiltration membranes, the effect of the addition of dichloromethane and poly(vinyl pyrrolidone) in a casting solution was investigated on the membrane performance. It was observed that the addition of dichloromethane increased the solute rejection rate. By changing the ratio between polymer and poly(vinyl pyrrolidone), membrane performance could be controlled. Negatively charged sulfonated polyethersulfone could reduce fouling at higher or lower pH than isoelectric point of protein bovine serum albumin. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 2046–2055, 1999     

Synthesis of novel high oil‐absorption resins of poly(methyl methacrylate–butyl methacrylate) by surface‐initiated atom transfer radical polymerization using activators regenerated by electron transfer for efficient removal of oil

Oil‐absorption resins are considered one of the effective materials to separate organic chemical compounds from oily water. In this work, well‐defined high oil‐absorption resins of poly(methyl methacrylate–butyl methacrylate) grafted onto silica gel were prepared by surface‐initiated atom transfer radical polymerization using activators regenerated by electron transfer mediated by FeCl₃/iminodiacetic acid. The grafted polymers were grown in a controlled manner. By considering the effect of different polymerization conditions, we prepared novel high oil‐absorption resins. The chemical structures of the resins were determined by Fourier transform IR spectroscopy. SEM and TGA were also used to characterize the resins. It was found that the resins had good heat‐resistant quality, higher oil absorbency and better oil retention and regeneration properties. The resins can absorb 31.2 g g^?1 for tricholoromethane and 23.3 g g^?1 for toluene. Copyright © 2012 Society of Chemical Industry     

Novel Flower-Like ZnO Hybridized with Acrylic Ester Resin for Enhanced Oil Absorption Properties

The acrylic ester resins have potential applications in for treatment of oily wastewater due to their high oil retention capacity and excellent cycle performance. Herein, a novel acrylic ester hybrid resins composed by poly(n-butylacrylate-co-styrene) resins and flower-like ZnO clusters were prepared using a combination of hydrothermal and suspension polymerization. The hybrid resins can remove a broad variety of oils from water with the maximum oil absorption performance of 30.87?g/g. More importantly, the hybrid resins are reversible and maintain high oil absorption properties after oils absorption-regeneration, making them promising candidates for treatment of oily wastewater.     

Engineering design of outer‐selective tribore hollow fiber membranes for forward osmosis and oil‐water separation

Outer‐selective thin‐film composite (TFC) hollow fiber membranes offer advantages like less fiber blockage in the feed stream and high packing density for industrial applications. However, outer‐selective TFC hollow fiber membranes are rarely commercially available due to the lack of effective ways to remove residual reactants from fiber's outer surface during interfacial polymerization and form a defect‐free polyamide film. A new simplified method to fabricate outer‐selective TFC membranes on tribore hollow fiber substrates is reported. Mechanically robust tribore hollow fiber substrates containing three circular‐sector channels were first prepared by spinning a P84/ethylene glycol mixed dope solution with delayed demixing at the fiber lumen. The thin wall tribore hollow fibers have a large pure water permeability up to 300 L m^?2 h^?1 bar^?1. Outer‐selective TFC tribore hollow fiber membranes were then fabricated by interfacial polymerization with the aid of vacuum sucking to ensure the TFC layer well‐attached to the substrate. Under forward osmosis studies, the TFC tribore hollow fiber membrane exhibits a good water flux and a small flux difference between active‐to‐draw (i.e., the active layer facing the draw solution) and active‐to‐feed (i.e., the active layer facing the feed solution) modes due to the small internal concentration polarization. A hyperbranched polyglycerol was further grafted on top of the newly developed TFC tribore hollow fiber membranes for oily wastewater treatment. The membrane displays low fouling propensity and can fully recover its water flux after a simple 20‐min water wash at 0.5 bar from its lumen side, which makes the membrane preferentially suitable for oil‐water separation. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4491–4501, 2015     

Performance of Nanofiltration Membranes for Solvent Purification in the Oil Industry

The extraction stage of edible oil in the oil industry is commonly performed by using toxic solvents (e.g. hexane) and processes with high energy consumption (e.g. distillation, evaporation) to recover the solvent, which represents around 70–75 wt% in the oil–solvent mixture. In this paper, a membrane-based extraction method using nanofiltration (NF) membranes is presented. Commercial nanofiltration membranes made of different polymers (Desal-DK-polyamide NF from GE-osmonics^®, NF30 polyethersulfone NF from Nadir^®, STARMEM^TM122 polyimide from MET^® and SOLSEP NF030306 silicone base polymer SOLESP^®) were selected and tested to recover the solvent from soybean oil/solvent (10–20–30% w/w oil) mixtures at various separation pressures and constant temperature in a dead-end filtration set up. The selection of the solvent was made in order to compare solvents obtainable from renewable resources, such as ethanol, iso-propanol and acetone, with solvents traditionally used in the industry (i.e. cyclohexane and n-hexane). The structural stability of the membranes towards the different solvents used in this work was verified visually, by the variation of the membrane area and by means of permeate flux assessments. Desal-DK and NF30 showed poor filtration performance and even visible defects after exposure to acetone but a good performance was obtained for the nanofiltration membranes STARMEM^TM122 and SOLSEP NF030306 with ethanol, iso-propanol and acetone. For example, considering a mixture with 30% edible oil in acetone, STARMEM^TM122 shows a flux and oil rejection of 16.8 L m^?2 h and 70%, respectively. For the same conditions, SOLSEP NF030306 exhibited a flux of 4.8 L m^?2 h with 78% rejection, which shows the potential application of nanofiltration membranes in the oil industry.     

Photodegradation of imidacloprid insecticide using polyethersulfone membranes modified with iron doped cerium oxide

The widespread accumulation of insecticides in water systems is a growing concern. This study reports efficient photodegradation of imidacloprid (IMD) insecticide using polyethersulfone (PES) membranes modified with iron-doped cerium oxide (Fe-CeO₂). The work focuses on the modification of ultrafiltration polyethersulfone membranes with incremental amounts of Fe-CeO₂ photocatalysts (0.5–2.0 wt.%) using phase inversion method. An increase in Fe-CeO₂ content showed an improvement in surface roughness and porosity of membranes. Pure water flux (PWF) increased from 55.9 L m² h⁻¹ in M0 (PES) to 77.2 (M1, 0.5% Fe-CeO₂-PES), 118.0 (M2, 1% Fe-CeO₂-PES), 128.0 in M3 (1.5 wt.% Fe-CeO₂-PES) and then decreased to 98.5 L m² h⁻¹ in M4 (2 wt.% Fe-CeO₂-PES). This decrease is brought about by the high Fe-CeO₂ content, which minimizes the membranes' surface pores. Fe-CeO₂ photocatalysts are thought to give the membrane both hydrophilic and photocatalytic qualities because of their capacity to absorb light and create radical species that cause the photodegradation of IMD molecules. Consequently, under visible light irradiation, modified membranes demonstrated photocatalytic ability over IMD. Photocatalytic efficiencies of the membranes were found to be 5.2% (M0), 68.9 (M1), 75.8 (M2), 81.8 (M3), and 56.0% (M4), respectively, with M3 membranes showing the highest photocatalytic degradation efficiency and low leaching of metals. The remarkable performance observed by M3 membranes during both water filtration and photocatalytic performance may be an illustration of well dispersed photocatalyst which receives high absorption of light irradiation. Membranes with photocatalytic functionalities are tailored to exploit dual benefits of the membrane filtration and photocatalysis without compromising their original functions. However, maintaining the delicate balance of this phenomenon is still very challenging.